1. Technical Field
The present invention relates to a synthetic resin retainer for a ball bearing, which is configured to retain balls in a freely rollable manner, and to a ball bearing having the retainer interposed between an outer race and an inner race.
2. Background Art
Various sealed ball bearings, such as a deep groove ball bearing and an angular contact ball bearing, are widely used, for example, for a gear support shaft of a transmission of a vehicle including an engine.
A ball bearing of this type includes an inner race having a radially outer surface formed as an inner raceway surface, an outer race arranged on an outer side with respect to the inner race and having a radially inner surface formed as an outer raceway surface, and a plurality of balls interposed in a freely rollable manner between the inner raceway surface of the inner race and the outer raceway surface of the outer race. A retainer is arranged between the inner race and the outer race so as to equiangularly retain the balls. Further, seal portions are arranged in an annular space formed between the inner race and the outer race. Any one of the outer race and the inner race is mounted to a fixed part such as a housing, and another is mounted to a rotary part such as a rotary shaft.
In particular, in electric vehicles and hybrid vehicles, high-speed motor rotation is input, and hence the rotary part such as the rotary shaft tends to perform high rotation. As a result, there arise problems such as deformations of a retainer due to a lack of lubrication, torque (heat generation), and to a centrifugal force. The deformations of the retainer due to the lack of lubrication and the torque (heat generation) can be solved by appropriately designing a shape of the retainer. Further, the deformation of the retainer due to the centrifugal force can be suppressed by using a lightweight synthetic resin retainer. Meanwhile, ball bearings for automotive auxiliary electrical components (such as a motor and an alternator) are used under a state of being sealed from both sides, and hence a lubricant such as grease needs to be used.
There have been proposed various lightweight synthetic resin retainers for the purpose of suppressing the deformation of the retainers due to the centrifugal force (for example, refer to Patent Literature 1). The retainer disclosed in Patent Literature 1 is what is called a resin crown-shaped retainer including an annular main part, and pairs of elastic pieces equiangularly and integrally projected at intervals on one side in an axial direction of the main part. Then, pockets each opened to a radially outer side and a radially inner side are formed respectively between the pairs of elastic pieces, and balls are retained in the pockets in a freely rollable manner.
Further, as a countermeasure against the torque (heat generation) and in order to use the retainer irrespective of the axial orientation of the bearing, it is preferred that the retainer be formed into a symmetrical shape in the axial direction. Thus, it is essential to provide a structure for coupling separate retainers to each other. Under the circumstances, there have conventionally been proposed various retainer structures for coupling two annular members to each other (Patent Literatures 2 to 6).